A new study from the Yale School of Public Health finds that an anti-smoking provision in the health law is discouraging people from signing up for insurance while simultaneously failing to get them to kick the habit.

Under the Affordable Care Act, individual health insurance plans sold on statewide marketplaces can only set how high their premiums are based on three factors: a customer’s geographic region, age, and smoking status. This is meant to let health insurers adjust their prices for how much medical care an enrollee may wind up using.